The present invention relates to a two-loop coiled type clamping device for semipermanently fasteningly fixing a fluid conveying hose, dustproof bellows, shaft coupling boot or some other article to be fixed made of a plastic material, such as rubber or synthetic resin, to the connecting circumferential surface of optional equipment.
As for this kind of two-loop coiled type clamping device, I have already obtained Japanese Utility Model Publication No. Hei 7-50631 and Japanese Patent Nos. 2898613 and 2947466, which are improved versions thereof, and U.S. Pat. No. 5,797,168, European Patent No. 0828107, Chinese Patent No. ZL 97116269. 7, Korean Patent No. 236726, and Thai Patent No. 11823, with priority claimed on the basis of said two Japanese Patents.
To cite said Japanese Patent No. 2898613 as an representative example, as described in the specification and drawings thereof, a clamp band 11 of metal strip material M of fixed length L is roll-bent for three-dimensionalization in an overall two-loop circular coiled state in which an inner overlap portion 11a which forms one roll-bent end side and an outer overlap portion 11b which forms the other roll-bent end side overlap each other in three layers by a fixed amount L through an intermediate overlap portion 11c. 
Therefore, as compared with a clamping device constructed such that it is simply roll-bent for three-dimensionalization as a single circular ring with overlapping taking place only in two layers partially by a fixed amount X (for example, Japanese Patent No. 2652136 and Japanese Utility Mode Publication No. Hei 7-47671 that I have proposed), there are advantages that the bore diameter of the clamp band 11 can be lightly and smoothly contractively deformed with a draw operating force (tightening torque) which is as low as only half and that, furthermore, an article to be fixed 10 can be stably fasteningly fixed to the connecting circumferential surface 32 of optional equipment 31, in a uniform overall surface close contact state, by means of the clamp band 11 which maintains a very high degree of circularity.
Further, in said known inventions, the clamp band 11 has an external contact region X1 and an internal contact region X2 which are held in a two-layer overlap state, and a plurality of float leg pieces 23 which are cut up in an inwardly bent state from an external contact region X1 are elastically contacted with an internal contact region X2 out of the two, the external and internal contact regions X1 and X2, or reversely, a plurality of float leg pieces 23 which are cut up in an outwardly bent state from the internal contact region X2 are elastically contacted with the external contact region X1, thereby causing said clamp band 11 itself to store a diametrical expansion/contraction spring force.
Therefore, even if the article to be fixed 10 is a dustproof bellows or shaft coupling boot made of rigid synthetic resin material, which has originally no elasticity, or even if the article to be fixed 10 is a fluid conveying hose made of elastic rubber material and happens to lose its elasticity due to aging as time passes, the article to be fixed 10 can be fasteningly fixed to the connecting circumferential surface 32 of optional equipment 31, always in a uniform overall surface close contact state, by the action of the clamp band 11 of absorbing changes in the rigidity and thickness of the article to be fixed 10 with said float leg pieces 23 serving as the expansion/contraction spring elements of the clamp band 11. Furthermore, it may be said that keeping the overall flat state provides the advantage of being usable with equipment, such as vehicles subjected to turning forces, vibrations, and shocks, without any trouble.
As the result of my intensive repeated studies, however, it has been found that with the arrangement of said known inventions, by the fixed amount X of intermediate overlap portion 11c in which the inner and outer overlap portion 11a and 11b of the clamp band 11 basically remain in a three-layer overlap state irrespective of the presence or absence of the float leg pieces 23 serving as the expansion/contraction elements of the clamp band 11, a first fixing tooth 18 bent out in an inwardly recessed state from the outer overlap portion 11b and a second fixing tooth 22 bent out in a reverse or outwardly raised state from the intermediate overlap portion 11c seizure-wise engage each other, thereby fasteningly fixing the clamp band 11 in a circular coiled state; since said second fixing tooth 22 is not disposed in the inner overlap portion 11a, the following problems arise.
That is, it is, as it were, the fate of the clamping devices disclosed in said known inventions that when the inner and outer overlap portion 11a and 11b of the clamp band 11 are drawn by a draw type operating tool P, the first and second fixing teeth 18 and 22 once move across each other and after this move-across, they seizure-wise engage each other, such relation resulting in the seizure-wise engaged state (the fasteningly fixed state of the article to be fixed 10) being afterward slacked by an amount corresponding to the spring-back after said move-across.
In this respect, the arrangement of said known inventions is such that the second fixing tooth 22 is bent out in an outwardly raised state from the intermediate overlap portion 11c to seizure-wise engage the first fixing tooth 18 of the outer overlap portion 11b in the first lap of the clamp band 11; therefore, the clamp band 11 is no different in terms of a mechanical fasteningly fixing means for the clamp band 11 from a one-loop clamping device. Thus, in spite of being a two-loop coiled type clamping device, said post-slack still frequently occurs.
Then, if the article to be fixed 10 is a thick-walled fluid conveying hose or the like made of elastic rubber material, it is capable of absorbing said amount of slack by its thick-walled elastic material, whereas if the article to be fixed 10 is a thin-walled protective bellows, shaft coupling boot or the like particularly formed of inelastic rigid synthetic resin material, said amount of slack leads to a fatal defect for the clamping device.
For example, with the amount of seizure engagement of said first and second fixing teeth 18 and 22 being 0.5 mm, suppose mutual move-across by a greater amount of 0.6 mm. Then, the first and second fixing teeth 18 and 22 spring back by an amount of about 0.19 mm in calculation along the circumference of the clamp band 11. The amount of such post-slack of about 0.19 mm is an excessive numerical value for the article to be fixed 10 such as a protective bellows, shaft coupling boot or the like which is usually formed about 1.0–1.5 mm thin-walled from rigid synthetic resin material, with the result that it happens that the stable firm tightened state of the article to be fixed 10 cannot be obtained.
Further, in the case where the clamp band 11 is produced on a multiproduct production basis with the bore diameter varying according to the diameter of the article to be fixed 10, the distance between said first and second fixing teeth 18 and 22 has to be changed. However, since the second fixing tooth 22 is bent out in an outwardly raised state from the intermediate overlap portion 11c of the clamp band 11, the calculation of accurately determining the bending-out process position is very difficult to the extent that even a slight positional deviation makes it impossible to firmly stably tighten the second fixing tooth 22 to the first fixing tooth 18 of the outer overlap portion 11b, in which sense also the clamping device becomes fatally defective, detracting from the economics of multiproduct mass production.
Further, in the case of this kind of a two-loop coiled type clamping device, in comparison with a one-loop type, the inner and outer overlap portions 11a and 11b have to be subjected to an additional drawing operation by an amount corresponding to the clamp band 11 being in two-loop roll-bent three-dimensional form. With the arrangement of said known inventions, however, since the place where the first and second fixing teeth 18 and 22 seizure-wise engage each other is only one place in the clamp band 11, without having no temporarily fixing means, it is necessary to contractively deform the clamp band 11 at one effort until the intended final bore diameter is attained. Such drawing operation can hardly be performed lightly and, moreover, if misengagement should happen, this would cause the clamp band 11 to energetically springingly spread out, involving the danger of hurting the operator.